This application relates generally to a power or manual seat adjustment assembly for adjusting the height of a seat within a vehicle. More particularly, this invention relates to a vertical seat adjuster having a torque tube and linkage assembly for engaging a stop to move the seat between maximum lowered and raised positions.
Seat adjustment assemblies for adjusting seat position within a vehicle are generally well known. Most arrangements provide for a seat to be moved or adjusted in forward and rearward directions within a vehicle. In many circumstances, it is desirable to have a seat adjustment assembly that can vertically move a seat between lowered and raised positions. Such an arrangement is necessary, for example, to accommodate vehicle drivers that are of varying heights. These seat adjusters can be manually/mechanically controlled or can be electrically controlled.
Electrically controlled adjustment assemblies typically include a vertical drive mechanism that includes a motor, a spindle or threaded drive shaft, a drive nut, and a drive link connecting the shaft to a torque tube. The motor drives the nut to move the shaft, and the drive link takes the linear movement of the shaft and provides rotational input to the torque tube. A linkage assembly is used to connect the torque tube to a seat bottom, and as the torque tube rotates, the linkage assembly causes the seat bottom to move vertically.
The seat bottom travels between two extreme positions, a maximum lowered position and a maximum raised position. The total vertical distance of travel between these two positions can vary depending on design requirements. However, in order to ensure maximum operating efficiency for the vertical drive mechanism, it is preferable to have the drive shaft and the drive link at a ninety degree angle with respect to each other when the seat bottom is at a mid-adjustment position, i.e. at a distance half-way between the maximum lowered and raised positions. In order to maintain this same orientation for seats having different total vertical travel distances, the length of the drive shaft is changed. This is expensive because it causes proliferation of parts.
Sometimes, a collar or sleeve is placed on the shaft to limit vertical travel distance. This allows the same shaft to be used for seats having different total vertical travel distances. The collar or sleeve is simply positioned at a location on the drive shaft that corresponds to the maximum desired vertical travel distance. The disadvantage with this configuration is that the drive shaft and drive link are not always maintained at a ninety degree angle with respect to each other at the mid-adjusted position. Thus, it is desirable to have a vertical adjustment mechanism that can utilize a single drive shaft for seats having different total vertical travel distances that maintain a ninety degree relationship between the shaft and the drive link at the mid-adjust position.
Sometimes a nut and spring washer are mounted on the drive shaft to serve as a stop to define the maximum raised and lowered positions. One disadvantage with this configuration is that the nut over-tightens at the maximum adjusted positions. This can cause what is know as lock-up or a sticking condition, which makes it more difficult to move from the maximum adjusted position to another vertical seat position. Thus, it is desirable to have vertical adjustment mechanism that eliminates lock-up and sticking during adjustment. The mechanism should also reduce the number of required parts, improve ease of assembly, and maintain or improve the operating efficiency of the drive system.